Sludge is a by-product of paper-making processes which has relatively limited uses and can present difficult and sometimes costly disposal problems. Recycled paper tends to contain more sludge-forming components than conventional virgin fiber sources. Substantial growth in the use of recycled paper has generally increased the amount of sludge generated.
In the past, sludge has typically been burned or buried. Those alternatives may pose environmental risks and can be relatively expensive. Some attempts have been made to incorporate small portions of sludge into papers made out of more conventional paper-making pulps. These efforts may be suitable for sludge material which is somewhat fiber-like and contains relatively low levels of ash-generating materials (e.g., clays, fillers, dirt and the like). Paper-making sludge which contains relatively high levels of ash-generating materials can present special problems.
Thus, there is a need to find a practical use for paper-making sludge which contains relatively high levels of ash-generating materials. A need exists for a practical process for converting paper-making sludge into a useful material or component of a product. There is also a need for a material or component of product which is made from or contains a substantial amount of paper-making sludge, especially a material or component made from or containing paper-making sludge that has relatively high levels of ash-generating materials.